C(3) Functional Derivatives of the Blatter Radical

Abstract

A series of 3-substituted 1-phenyl-1,4-dihydrobenzo­[e]­[1,2,4]­triazin-4-yls 1 was prepared by addition of PhLi to 3-substituted benzo­[e]­[1,2,4]­triazines 2 followed by aerial oxidation. The scope of the C(3) substituents in the reaction was investigated, and 10 structurally diverse radicals 1 were isolated, their stability was assessed and properties were investigated with spectroscopic and electrochemical methods. Two radicals were analyzed with single-crystal XRD methods. Experimental data are compared to DFT results and correlated with Hammett substituent parameters.

Functional Planar Blatter Radical through Pschorr-Type Cyclization

“…14,24,25 Of particular interest in this context are the prototypical Blatter radical 26 [A (Figure 1)] and its derivatives. 27,28 Their exceptional stability, spin delocalization, and attractive electrochemical 29,30 and photophysical 31 properties have recently been explored in the design of molecular electronics, 8 controlled polymerization, 32 and magnetic 33 and spintronic applications 15 and also for studies of high-spin molecular systems 34−36 and photoconductive liquid crystals. 37−40 A common feature of N(1)−aryl derivatives of radical A is the large torsion angle of the aryl group, 41 which affects the molecular packing.…”

“…Experimental a N hfcc (Figure 4 and the Supporting Information) are consistent with those for other benzo[e]-[1,2,4]triazinyl radicals. 29,30,47 Analysis of the results indicates that the a N(12) value decreases (from 7.49 G for 1h to 6.88 G for 1d), while values for a N(1) and a N(3) increase {from 4.08 G [a N (1) ] for 1h to 4.57 G [a N (1) ] for 1d} with an increase in the electron withdrawing character of the C(10) substituent. This is consistent with destabilization of the dipolar resonance form in the triazine ring needed to enable delocalization of spin density onto the "upper" benzene ring.…”

“…Organic radicals with π-delocalized electron spins are rapidly becoming important building blocks for modern functional materials for energy storage, − molecular electronics, − memory devices, − spintronics, − organic batteries, light-emitting diodes, , quantum information processing, biophysical applications, − and other applications. ,, Of particular interest in this context are the prototypical Blatter radical [ A (Figure )] and its derivatives. , Their exceptional stability, spin delocalization, and attractive electrochemical , and photophysical properties have recently been explored in the design of molecular electronics, controlled polymerization, and magnetic and spintronic applications and also for studies of high-spin molecular systems − and photoconductive liquid crystals. − A common feature of N(1)–aryl derivatives of radical A is the large torsion angle of the aryl group, which affects the molecular packing. This, in turn, determines the type and strength of spin–spin interactions and semiconductive properties and is unfavorable for induction of liquid crystalline properties.…”

Recent advances in the chemistry of benzo[e][1,2,4]triazinyl radicals

“…Sensitive functional groups, such as halogens or competitive acceptors such as carbonyl-containing groups, are not expected to perform adequately in these systems, adding some limitations to the preparative scope of Scheme 14. This said, recent developments in benzotriazine synthesis has enabled access from 42 to a variety of novel, 3functionalised Blatter radicals (43, Scheme 15), 64,65 not easily accessible by any alternative method discussed here. Scheme 16.…”

“…Time-dependent density functional theory (TD-DFT) calculations have been conducted by several authors in order to characterise these features. 57,64,88 While the major absorption in the UV region can be attributed to a predominately HOMO-1 to LUMO transition, the SOMO to LUMO transition is barely visible in most examples due to its low oscillator strength, a result of poor SOMO-LUMO overlap. Fluorescence emission studies of Blatter's radical 9 have also been conducted by Itskos and Hayes et al 88 Under UV (270 nm) excitation in the solution phase, a strong and narrow emission band was measured at 350 nm.…”